SOUTHERN AFRICA

Southern Africa is mostly semi-arid, and experiences variation in rainfall,
both over time and between countries. This sub-region is also expected to experience
further variability in rainfall, reduced precipitation and increased evaporation,
as a result of climate change. With a rapidly growing population, and demands
from the domestic, agricultural and industrial sectors for water, freshwater
availability is a priority concern for the sub-region. Discriminatory access
policies and pricing systems have also skewed the distribution of access to
water resources across population groups. An additional concern in the subregion
is declining water quality due to domestic and industrial pollution, and eutrophication
and salinization due to agricultural pollution.

AVAILABILITY OF FRESHWATER IN SOUTHERN AFRICA

Southern Africa’s annual average surface water resources are approximately
534 km3/yr, but they are distributed unevenly due to: frequently
low and variable rainfall; terrain; evaporation rates; and vegetation and soil
cover. For example, Angola, the wettest country in the sub-region, has average
annual internal water resources of 184 km3/yr (14 000 m3/capita/yr),
and Mozambique and Zambia have 100 km3/yr and 80 km3/yr
respectively (5 000 m3/capita/yr and 8 700m3/capita/yr).
By contrast, the driest countries, Botswana and Namibia, have just 2.9 km3/yr
and 6.2 km3/yr respectively (1 700m3/capita/yr and 3 500m3/capita/yr
respectively) (UNDP and others 2000).

The areas of low rainfall are in many cases also coincidental with areas of
highest evaporation potential, and variability in rainfall can result in periodic
episodes of severe and prolonged droughts, particularly in the southwest. In
these areas, groundwater resources are particularly important (see Box
2e.7). By contrast, the northern and eastern areas are subject to occasional
floods, the most recent example being in 1999–2000. The excessive rains of this
season affected Mozambique, Botswana, Zambia, Zimbabwe and South Africa. Some
200 000 ha of cropland were flooded and more than 150 000 families were affected.
The estimated cost of recovery is millions of US dollars (Mpofu 2000). Although
the SADC Early Warning System was able to predict the heavy rains, most countries
were ill-prepared for the magnitude and duration of the floods, stimulating
investigations and revisions of response strategies.

Box 2e.7 Importance of groundwater in Southern Africa

Groundwater is the main source of water for about 60 per cent of
both rural and urban residents throughout southern Africa. A large
part of the subregion is characterized by small towns, villages
and dispersed rural settlements. Thus, access to reticulated surface
water resources has been limited because of the high costs and long
distances that need to be covered in order to establish infrastructure
for formal water services. The sustainable management of groundwater
is, therefore, important for rural livelihoods in the sub-region,
even though the proportion of water coming from groundwater sources
is relatively small.

Source: Chenje 2000

Lake Malawi has the largest number of fish species of any lake in the
world, estimated at more than 500 species, of which 90 per cent are thought
to be unique to the lake. The most important species biologically, and
in terms of local livelihoods, are the 400 or more cichlid species, of
which all but five are endemic to Lake Malawi

The sub-region’s largest freshwater lake, and the third largest lake in Africa,
is Lake Malawi, with a surface area of 31 000 km2. The lake is important
in terms of fishing activities and the tourist industry which it supports. Lake
Malawi has the largest number of fish species of any lake in the world, estimated
at more than 500 species, of which 90 per cent are thought to be unique to the
lake. The most important species biologically, and in terms of local livelihoods,
are the 400 or more cichlid species, of which all but five are endemic to Lake
Malawi (Ribbink, Marsh, Ribbink and Sharp 1983). Because of this extraordinary
biodiversity, the southern part of the lake is registered as a national park,
and was established as a Natural World Heritage Site in 1984. Major rivers include
the Zambezi River, whose basin is shared by eight southern African countries
and is home to 40 million people. The Zambezi basin also supports many local
communities, as well as commercial agriculture and forestry, manufacturing and
mining, conservation and tourism (Chenje 2000).

A study of the potential impacts of climate change on freshwater resources
in southern Africa predicts an overall reduction in rainfall, by as much as
10 per cent across the whole sub-region, and up to 20 per cent in parts of South
Africa (WWF 2000). Evaporation rates will increase by 5–20 per cent, as a result
of raised temperatures, which will reduce run-off, and decrease water security
and agricultural potential. Coincident with this will be increases in the frequency
and intensity of flooding and drought (WWF 2000). In addition to variability
and long-term decline in precipitation, water resources development is further
complicated by the uneven distribution of population—particularly, high population
densities in arid areas. Per capita average annual water resources in Angola,
for example, exceeds 14 000 m3/capita/yr whereas, in South Africa,
each person has only slightly more than 1 000 m3 per year (UNDP and
others 2000).

Environmental degradation is a further contributor to decline in water availability,
through loss of vegetation, and the disruption of microclimates and hydrological
cycles. Dense stands of alien vegetation in southern Africa are particularly
disruptive in this regard, because they use much larger amounts of water than
indigenous species (see Box 2e.8). In some areas of southern
Africa, up to 50 per cent of wetlands have been transformed, and the Caprivi
wetland system (Namibia) has been reduced to almost 25 per cent of its original
size. This has been due to: draining of wetlands, for agricultural or infrastructure
development; reduced flows; aquatic weeds choking water courses; increasing
use of pesticides; and overextraction of reeds, wood and other materials for
construction, weaving and crafts (Chenje 2000). Wetlands act as sponges, absorbing
excess water in times of heavy rainfall and, thus, buffering the effects of
flooding. To prevent further degradation of these important habitats, two countries
of the sub-region, South Africa and Zambia, are parties to the 1971 Ramsar Convention,
and have designated certain areas as Wetlands of International Importance.

Box 2e.8 Alien invasive vegetation and water use in southern
Africa

Alien invasive vegetation is a significant and growing problem
in many areas of southern Africa, especially in riparian zones.
The water hyacinth (Eichornia crassipes) is choking many
water bodies in South Africa, Swaziland, Malawi and Zimbabwe, and
exotic timber species, such as pines (Pinus sp.) wattles
(Acacia sp.) and eucalypts (Eucalyptus sp) take up
more water than indigenous species, thereby reducing mean annual
run-off. Zimbabwe and South Africa have initiated biological and
chemical control programmes for the water hyacinth, with some success
to date. South Africa’s Working for Water Programme, launched in
1995, is a nationwide alien plant control programme, building capacity,
and generating employment and incomes among some of the country’s
poorest communities. The programme uses mechanical, chemical and
biological control methods and, during 2000, the teams cleared 238
000 ha and rehabilitated 51 000 ha of land which was infested with
alien vegetation. The activities of that year employed 21 000 people.